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Feb. '28, 1.9332 j l E. c. BRlTToN ETAL. v 1,899,257

PRooEss FOR THE PURIFICATION oF DIPHENYLOXIDE Filed March 3, 1932 Vacuum Stall Fig. 2 INVENTORS f w @www H4 BY wm E. fw(

474.94% ATTORNEY PatentedlF eb. 128,. 1933i anser c BRITTONANDWILLIAM R. REED, on MIDLAND, MIcHiG'Al-v, Assisnoas fro THE nowci-rnrfrrcnn ooivrrnnior MrnLANnivricHrGn-N. A con-rcsi-z riroiv;k or MICHIGAN;`

'rRocEss FORTHEPUIFICATION oF DIPHENYLOXIDE Application i filed. March l3,

The invention relates toa process for the purification of `diphenyloxide byk crystallization from a solution insa solvent medium andniore particularly tofa process `wherein '5 methyl alcohol is used asa solvent.

Ordinary Lmethods Vfor `the preparation of diphenyloxide yield aproduct containing impurities such as monochlorobenzeneynaph-- thalene, and hydroxy 'diphen'yh from ywhich. i the; diphenyloxidel can nothbe completely ireedzby distillation. Crystallization from a solvent is the other common method for `the puriiication of organic compounds, but-in the case of diphenyloxidethis is lrendered diili-f ;-cult or impractical by the extreme solubility of diphenyloxide inmost lorganic solvents.

The use of ethyl alcohol has been'proposedl inl connection?l with vlaboratory methods 4for the purification of diphenyloxide. However,.'

i ethyl alcohol becomessaturated with' diphenyloxide kat a relatively low'r temperature and.

atv higher temperatures itY forms liquid mixtures withy diphenyloxide from'whichthe vdif phenyloxide can not be crystallized.

,25' Ne have Vfound .that methyl alcohol is largely free from theylimitations of ethyl alcohol becausel it does not form non-crys-A ing and the 'following description vsetting forth in detaily one modeof carrying outthe invention, such disclosed mode illustrating,

however, but one of the various ways in which the principl'efof the invention may be realized.

In said annexed drawing Figure 1 shows the solubility curve of diphenyloxide in methyl alcohol` and in ethyl alcohol. FigureV 2 'is a flow sheet representing diagrammatically the lowof'materia-ls through apparatus adapted to Vcarry out our process. y v y Referring to Figure 1, the/dotted line curve shows the sol lbility of diphenyloxide inethyl alcohol. `PointA onthis curye represents the upper. limit of truev solubilityjof To the foregoing yand relatedl ends,the invention, then, consists in the methodhere- 1932. serial No. 596,558.-

d'ephenyloxideiin ethyl alcohol. This upper limit is about 115 grams of diphenyloxide per. 100 milliliters of ethyl alcohol, anda solution prepared invthis .ratio will yield, upongcooling below `22" C., purilied crystals of diphenyloxide.- For instance, .cooling a solution of 115 grams of `diphenyloxide m10() milliliters of ethylalcoholto about 109 C.

will precipitate about 100 vgrams of diphenyloxidecrystals. However, it is impossible to'obt'ainl larger yields of diphenyloxide ycrystalsperlOO milliliters of ethyl alcohol, be-

cause',"while,it is possiblel to-form liquid mixy tures. containing more than 115 grams of diphenyloxlde per-'10() milliliters of ethyl alcohol` at temperaturesV above 22o C., Vas such amountgof diphenyloxide in rexcess of the aforesaid ratio will separate-as ani oil 'in stead ofaslcrystals, -and the oil will retainv liquid mixtures arecooled back to 22 C.v anyy they impurities 'contained inthe original di.- phenyloxide. The use` of ethyl alcohol as a y n solvent forpurlfying diphenyloxide is thereforelimited in that the maximum ratio that can be used effectively is 115 grams of diphenylox-ide per-.100 milliliters vof ethyl alcohol. On. the other hand, the ysolid linermeth'yl alcohol solubility kcurve shows that at least,-`

25,0 grams of diphenyloxide can be dissolved ltrue solutionfrom which the diphenyloxide in lOOmilliliters of methyl alcohol to formV a will crystallize readily as a solid upon lowering the temperatureof the solution.' Forfinv,

stance, 250gra1ns of -diphenyloxide can be dissolvedv in milliliters of methyl alcohol at `about 23C.' and upon cooling the solution to about 10 C. over 23o grams of difphenyloxide lcrystals .will precipitate. k-It' is therefore*Y apparent that considerably'` more 'than twice the amount-of diphenyloxide canv be. crystallized from methyll alcohol as .can be crystallized froman'e'qual amount of ethyl alcohol.y lThe signilicance ofthis lies intheY fact that less than one-half the amountfof methyl alcohol will be required forfrecrystallizing a givenamount of diphenyloxide used as the solvent. l

that would be-required ethyl alcohol were Referring to Figure 2, the flow-'of materials ythrough anvapparatus suitable forcarrying.

out ourl process will be described.` CrudeV vdiphenyloxide is introduced, along with Vdue to the supercooling of thesolution.` The solution is preferably'to be cooled slowly and .agitated during the cooling period. When a temperature between l5-21 C., preferably about 18 G., is reached, the solution may be seeded-with pure diphenyloxide crystals. As

the crystals separate the temperature of the solution rises almost immediately to `21.5" C. The mass is thencooled to about10 C. to precipitate a further quantity of the diphenyloxide crystals, after whichthe crystals are removed' in a slurry of mother liquor to a centrifugal extractor wherein the mother liquor is removed yandpassed intoa methyl alcohol recovery still.` The methyl' alcohol from the still is recycledjto the crystallizer.`

The crystals from vthe extractor are preferably to be further purified Vandany occluded motherliquor' separated therefrom, bydis-` tilling under reduced pressure, e.g. between 25 to 7 5 `millimete rs ofv mercury absolute. By this method crystals of diphenyloxide having a vpurity above 199 per cent areobtained. v

A further advantage accrues to our process by virtue of the fact that diphenyloxide can be crystallized from methyl alcohol in the presence of substantial quantities of water, sayl about 7 per cent by volume, while the presence of' even as little as 3 per cent by volume of water in an ethyl alcohol solution' of diphenyloxide will cause 'the diphenyl-V oxide to precipitate as an oil instead of crystals when the solution is cooled. This assumes added significance when the point of Vcompletely freeing the solvent fromwater by distillation is" considered. Ethyl alcohol forms an azeotropic solution with water,'c on taining about 8 Vper Vcent of water by volume,

from which the water can vefficiently be removed only by chemicalaction. In contrast,

methyl alcohol can be completely freed of distillatiom y VVOthermodes of applying the principle of water by the inexpensive `procedure of simple our invention' may be employed instead-of the one explained, change eing made'as regards the process herein disclosed, provlded 2; In a process for the purification of crude diphenyloxide, the steps which consist in formin a solution of crude diphenyloxide in `met yl alcohol, cooling said solution to precipitate diphenyloxide crystals, and separating said crystals from the solution.

3f In a process for the purification of crude diphenyloxide, the steps which consist in forming a solution of crude diphenyloxide in methyl alcohol, cooling said solution to precipitate.diphenyloxide crystals, separatingthe crystals from the solution, and distilling said crystals under reduced pressure.

4. In a process for the purification of crude diphenyloxide, the steps which consist in forming asolution by dissolving crude diphenyloxide in methyl alcohol at a temperature etween 23-30 C., cooling said solution to a temperature between 15-2l C. to

precipitate"diphenyloxide as crystals, separating said kcrystals from the mother liquor, distilling said mother liquor so as to recover the methyl alcohol and returning the sorecovered methyl-alcohol to the first step, and

distilling the said crystals Aunder Aa reduced pressure of between 25 Aand 7 5 millimeters absolute. v 1

i 5. In aprocess of recovering substantially pureV diphenyloxide from crude diphenyloxide, the steps which consist in forming a solution by dissolving crude diphenyloxide inabout 40per cent of its own volume of methyl alcohol at a temperature between 23-30 cooling said solution to a temperature of approximately 18 C.. seeding the so vcooled solution with pure diphenyloxide crystals, further cooling the solution to approximately 10 C. while' precipitating diphenyloxide crystals, separating said crystals from the mother liquor, distilling said mother liquor so as to recover the methylY alcohol, `returning the so recovered methyl alcohol tothe firststep, and further purifying said diphenyloxide crystals by distilling sameunder a reducedV pressure of between y25 and 75 millimeters of mercury absolute;v

` Signed by us this 23rd day of February EDGAR orBRrTToN.

t WILLIAM n.' REED.'

the step or steps stated byany ofthe followi ingclaims or the equivalent V of such stated step or steps be employed.

l/Ve therefore particularly point out an distinctly claim as our invention l. The processV for obtaining substantially pure diphenyloxide which comprises crystallizing diphenyloxide from solution in methyl alcohol. 

